Content of Frontier & focus: lightning monitoring and forest lightning fire dynamics in our journal

Published in last 1 year |  In last 2 years |  In last 3 years |  All Please wait a minute... For Selected: Download Citations EndNote Reference Manager ProCite BibTeX RefWorks Toggle Thumbnails Select Relationship between Lightning, Lightning Fire and Human Activities Liqing Si,Shangbo Yuan,Fengjun Zhao,Lifu Shu,Mingyu Wang,Qiming Ma Scientia Silvae Sinicae    2022, 58 (11): 1-9.   DOI: 10.11707/j.1001-7488.20221101 Abstract （319）   HTML （5）    PDF （1019KB）（78）       Knowledge map    Save Lightning is the main source of natural fire, and lightning fire and other types of forest fires together constitute the global forest fire system. It is generally believed that lightning fire, as a natural fire source, has nothing to do with human beings and is different from man-made fire sources, but in fact, human activities have inextricable links with the occurrence of lightning fire. Since 2019, due to the severe impact of COVID-19 lockdowns, non-essential activities and mobility have decreased, which has led to a significant decrease in pollutant concentrations and lightning. In this paper, we linked the lightning fire with modernization process of human beings, the expansion of habitation, the change of underlying surface, the development of prediction technology and firefighting technology, and the laws and regulations of the country, to explore the impact of human activities on the occurrences of lightning and the forest lightning fire. Lightning is the fire source of the three elements in lightning fire occurrence, the lightning that can cause lightning fire is mainly cloud-to-ground lightning. The human activities in recent decades have profoundly affected the content of aerosols in environment. Aerosols are the main factors affecting lightning, and the large amount of pollution aerosols emitted from urban areas, soot aerosols emitted from biomass combustion and urban heat island effect have all increased the probability of lightning occurrence. The average annual ground lightning density of different land cover types is obviously different, and the construction land has the highest average annual ground lightning density. Intense lightning in forest areas has a higher density and slope. Most of the forests are located in high altitude areas, which is consistent with previous studies showing high lightning frequency in high altitude areas. The lightning in forests is intenser, steeper and more destructive, so forest areas are prone to lightning strikes. Lightning has the characteristic of selective discharge, that is, it will discharge into some special areas, which are also known as lightning selection areas, such as the place groundwater is exposed to the ground, where different conductive soils are connected, and where there are underground metal mines, such as copper and iron mines, and underground lake and water reservoir areas. Lightning strikes are caused by changes in soil conductivity caused by human activities such as mining waste rock sites, reservoir construction on mountain tops, and power transmission lines in mountainous areas. At the same time, due to the abundant trees in the mountainous area, it is also important to avoid the resulting lightning fire. With the development of lightning monitoring technology, a lightning location monitoring system has been established in some areas of China. Especially in 2021, the National Forestry and Grassland Administration launched the "Enlisting and Leading" emergency science and technology project of forest lightning fire prevention and control, and the project team has constructed a lightning fire sensing system in the Daxing'anling region with three-dimensional lightning full-wave detection network as the main body, covering the forest area of the Daxing'anling forest region, which can accurately locate the location of cloud-to-ground lightning in real time, improve the monitoring and warning ability of lightning fires, and improve the efficiency of lightning fire discovery. National laws and regulations indirectly affect lightning fires by affecting forest cover and climate change. This paper is expected to provide reference for the occurrence, prevention and control of forest lightning fire in the future, and provide a basis for the formulation of corresponding policies. Table and Figures | Reference | Related Articles | Metrics Select Temporal and Spatial Distribution Characteristics of Lightning in Daxing'anling Mountains Based on VLF/LF 3D Lightning Location System Weike Li,Lifu Shu,Shangbo Yuan,Jiajun Song,Wei Li,Liqing Si,Fengjun Zhao,Yahui Wang,Mingyu Wang Scientia Silvae Sinicae    2022, 58 (11): 21-30.   DOI: 10.11707/j.1001-7488.20221103 Abstract （135）   HTML （2）    PDF （1771KB）（56）       Knowledge map    Save Objective: Lightning fire is the biggest cause threatening the safety of forest resources in Daxing'anling Mountains. This study aims to provide a scientific basis for lightning fire monitoring, early warning, prevention and suppression by analyzing the occurrence pattern of lightning in the Daxing'anling Mountains. Method: Based on the monitoring data with the VLF/LF 3D lightning location system from 2019 to 2021 in Daxing'anling Mountains, the quantity of lightning (intra-cloud lightning, IC; cloud to ground lightning, CG; positive lightning, PL; negative lightning, NL), current intensity, height of IC, and the temporal and spatial distribution of lightning activities were analyzed. Result: 1) A total of 710 487 times of lightning were detected in Daxing'anling Mountains (321 667 times in Heilongjiang Daxing'anling Mountains and 388 820 times in Inner Mongolia Daxing'anling Mountains) from 2019 to 2021, with an average of 236 829 times per year. The lightning in Daxing'anling Mountains was mainly negative CG, in which the IC: CG ratio and PL: NL ratio were roughly 1:5. The current intensity of PL and NL in Daxing'anling Mountains ranged from 4.5 to 371 kA, and from -501.7 to -4.5 kA, respectively, and the absolute value of the current intensity of most lightnings was concentrated between 4.5 and 50 kA. The average IC height in Daxing'anling Mountains was 4.72 km, of which 88.09% was mainly below 10 km. 2) The average number of lightning days in Daxing'anling Mountains was 127 days per year. Lightning started at the end of April and ended in mid and late October, mostly from May to August, of which July was a concentrated high incidence period. The occurrence of lightning showed a single peak change pattern in a single day. Lightning started to increase at 10:00, and the high incidence period was from 12:00 to 17:00. After 18:00, the number of lightning gradually decreased, and the total amount of lightning decreased significantly from midnight to early morning. 3) The distribution of lightning in Daxing'anling Mountains was spatial aggregation. On the whole, the lightning density in Daxing'anling Mountains of Heilongjiang was significantly higher than that in Daxing'anling Mountains of Inner Mongolia. High density lightning areas were mostly distributed in Daxing'anling Mountains of Heilongjiang, such as Huzhong, Tahe, Hanjiayuan, Xinlin, Nanwenghe Nature Reserve and Jiagedaqi. 4) Low intensity negative CGs, which are easy to cause lightning fires, were mainly concentrated in Xilinji, the south of Tuqiang, most area of Tahe, the north of Huzhong, and Nanwenghe Nature Reserve in Heilongjiang Daxing'anling Mountains, and the north of Mangui, a small part of Hanma and Jinhe in Inner Mongolia Daxing'anling Mountains. Conclusion: The occurrence of lightning in Daxing'anling Mountains has obvious spatial-temporal heterogeneity. Based on the occurrence pattern of lightning and specific types of lightning that are prone to fire, it is suggested that targeted monitoring, early warning and early deployment are effective means to prevent major lightning fires. Table and Figures | Reference | Related Articles | Metrics Select Process and Influencing Factors of Mass Lightning Fires Caused by Dense Lightning in Daxing'anling Mountains Mingyu Wang,Shangbo Yuan,Wei Li,Weike Li,Jiajun Song,Liqing Si,Yahui Wang,Fengjun Zhao,Xiaorui Tian,Xiaoxiao Li,Lifu Shu Scientia Silvae Sinicae    2022, 58 (11): 10-20.   DOI: 10.11707/j.1001-7488.20221102 Abstract （156）   HTML （5）    PDF （5244KB）（98）       Knowledge map    Save Objective: The occurrence of lightning fire is comprehensively affected by lightning, meteorological conditions, forest fuel, terrain, etc. Various factors are coupled and act together. After the launch of "forest lightning fire prevention and control emergency technology project", a full waveform three-dimensional lightning detection network covering the Daxing'anling Mountains has been built. Combined with the national basic meteorological station, lightning fire meteorological monitoring station, watchtower and ground patrol, the network can be used to carry out collaborative monitoring and early warning of lightning, weather and lightning fire occurrence. The number of mass lightning fires caused by dense lightning processes accounted for most of lightning fires in the spring fire season of 2022. Based on the data of the lightning fire sensing system, this paper aims to analyze the quantitative characteristics of various factors causing lightning fires, and clarify the mechanism of the influence of various factors in the dense lightning process on the occurrence of lightning fires. Method: Based on the lightning fire sensing system, the monitored lightning indicators, meteorological factors and lightning fire occurrence indicators were systematically analyzed. This study also analyzed the basic situation of lightning fire occurrence in Daxing'anling Mountains during the spring fire season in 2022, the impact of dense lightning on lightning fire occurrence, the quantitative characteristics of lightning that caused lightning fire, as well as the lightning location accuracy and lightning fire smoldering period. Result: In 2022, a total of 22 lightning fires occurred during the spring fire season in Daxing'anling Mountains, of which 18 were caused by dense lightning processes. The ground lightning and cloud lightning had one peak respectively in the positive and negative current area. The negative ground lightning accounted for 82.82% of the total number of ground lightning, and the ground lightning formed a high-frequency interval at -8~-50 kA. The number of lightning fires caused by negative ground lightning was the largest, which accounted for 70% of the total number of ground lightning, and accounted for 84.5% of the negative ground lightning. The positive ground lightning that formed a high-frequency range at 10~30 kA accounted for 12.7% of the total ground lightning, and 74.2% of the positive ground lightning, which was much lower than the number of negative ground flashes. The average current intensity of lightning fire in spring fire season was -22.72 kA, the strongest current was -48.34 kA, and the weakest current was -8.70 kA. The occurrence time of lightning that causes lightning fires was relatively concentrated, and lightning fires were mostly ignited around noon. There was a rapid temperature rise before the dense lightning that caused the lightning fire occurred. With the decline of air humidity and the increase of wind speed, the daily maximum temperature was basically the same as the occurrence time of the lightning that caused the lightning fire. It was also the period of time when the lowest relative humidity and the highest wind speed appeared. The smoldering period of lightning fire in spring fire season was from 0.56 to 17.62 h. The accuracy of lightning detection and location was 165~884 m, with an average accuracy of 394.5 m. There were two lightning fires with lightning wood positioning coordinates, and the positioning accuracy reached 165 m and 170 m. The fuels in the fire site were mainly waste mountain grassland, dry wetland meadow, as well as some coniferous forests, coniferous and broad-leaved mixed forests and burned slashes. Conclusion: The mass lightning fires caused by dense lightning processes account for the majority of lightning fires. The occurrence of mass lightning fires requires the coupling of dense lightning processes with extreme weather conditions of drought, as well as fuel available. When the lightning process is not synchronized with the precipitation process or the precipitation is less, and there is a rapid warming process in the early stage, and the intensive lightning process is accompanied by a drop in temperature, the lightning fires often occur in this period. In the process of lightning fire monitoring and early warning, we should pay special attention to the dense lightning process under drought conditions. Table and Figures | Reference | Related Articles | Metrics